Scott have you tried the stak client? Does does the KlausT client have equivalent performance?
The stak client ran a little bit slower IIRC. That it requires a config file to run (only command-line option is to specify the name of the config file) is also annoying.
In other news, I replaced the Asus Prime Z270-AR I had been using with an Asrock H110 Pro BTC+. I was hoping I'd finally get all three GPUs (two overclocked MSIs and a PNY) running on passive risers, but ended up putting the two MSI boards on the 4-port PCIe port multiplier I had been using with the other board:
http://www.ebay.com/itm/PCI-E-1-to-4-Ports-PCI-Express-16X-Slot-Power-Expansion-Riser-Card-Adapter-Board/132267216692I'm still running v17, but have downloaded v19. I think I'll throw that on a spare flashstick next and see if the passive risers work any better with it.